Lines of Symmetry Flashcards

All 6 cards in this deck

What is a line of symmetry of a 2D shape?

A mirror line: folding along it makes the two halves fit exactly onto each other.

How many lines of symmetry does a regular polygon with $n$ sides have?

e.g. a regular pentagon

$n$.

A regular pentagon has $5$ lines of symmetry.

How many lines of symmetry does a rhombus have, and where are they?

$2$ — along its two diagonals.

True or false? A parallelogram has two lines of symmetry.

False. A parallelogram (not a rectangle or rhombus) has no lines of symmetry, only rotational symmetry of order $2$.

How many lines of symmetry does an isosceles trapezium have?

$1$ — the line through the midpoints of the two parallel sides.

What does a line of symmetry of a polygon tell you about its sides and angles?

e.g. a kite

Sides and angles that reflect onto each other are equal.

In a kite the two angles either side of the line of symmetry are equal, so an unknown one can be deduced.